Rotary crushers are used in a variety of mining applications as well as in construction/demolition settings. A typical rotary crusher has a housing made of steel plate, a first fixed jaw and a second movable jaw positioned facing each other inside the housing. When the rotary crusher is actuated, the second movable jaw is urged to move between an open jaw setting (where the gap between the first end of the second movable jaw and the fixed jaw is at its greatest) and a closed jaw setting (where the gap between first end of the second movable jaw and the fixed jaw is at its smallest). When the second movable jaw in the closed jaw setting, a crushing force is delivered to the rock held between the jaws.
Different mechanisms have been used to actuate the movable jaw. One known mechanism employs a hydraulic motor and a drive belt and pulley arrangement operatively connected to a drive shaft. A pair of eccentrics is arranged on the drive shaft. Each eccentric is provided with a bearing. A hollow sleeve fixed to the movable jaw fits on the bearings and can freely rotate about the bearings. When the hydraulic motor is actuated, rotary motion is transferred through the drive belt and pulley arrangement to the drive shaft. As the shaft rotates, the eccentrics bear against the sleeve and a rotational/translational movement is imparted to the movable jaw thereby urging the movable jaw closer to fixed jaw to deliver the crushing force. Also provided is an adjustment mechanism for adjusting the cross-section of the discharge outlet of the crusher. The adjustment mechanism takes the form of a strut and one or more spacers interposed between the frame of the movable jaw and a portion of the crusher housing. A spring member holds the adjustment mechanism in place during the movement of the jaw.
Other known actuating mechanisms employ an arrangement of drive motor, eccentric shaft and toggle mechanism. The drive motor is connected to one end of the eccentric shaft, while a flywheel is rigidly fixed to the opposite end of the eccentric shaft. A pitman is held against the eccentric shaft and is arranged to bear against the toggle pin of the toggle mechanism. The toggle mechanism is defined by the toggle pin and a pair of opposed first and second toggle plates disposed in bearing engagement with toggle pin. Each toggle plate is mounted to extend between the toggle pin and a toggle seat. The toggle seat of the first toggle plate is carried on the crusher housing, while the toggle seat of the second plate is supported on the movable jaw. All the parts of the toggle mechanism are held firmly together by springs. When the crusher is actuated, the drive motor causes the eccentric shaft to rotate. The rotary motion urges the displacement of the pitman thereby causing the toggle plates to reciprocate and the movable jaw to pivot towards the fix jaw. A pull back spring mechanism is also provided to bias the movable jaw in the open setting position.
Crushers using the known jaw actuating mechanisms described above have tended to have only partial success in the field. While they tend to be generally effective at crushing softer rock in the range of 20,000 to 25,000 psi hardness, they have tended not to perform as well in applications requiring harder rock to be crushed. In some cases where attempts were made to crush harder rock using such crushers, the crusher mechanism lacked the requisite crushing power to crush the rock, and stalled. Worse still, in some extreme cases, the frames supporting the moving and fixed jaws flexed under the stress of crushing the harder rock, and failed.
Another drawback associated with these types of crushers is their inability to crush relatively large volumes of rock in a short period of time (i.e. that is more than 50 tons per hour), without substantially increasing the size of the crushing mechanism (and consequently, the cost of the crusher).
For reasons of versatility, it is desirable to have a crusher whose crushing mechanism is capable of being adjusted to produce crushed rock of a smaller or larger size, as required. While some of the crushers of the type described above have this capability, adjusting the crushing mechanism to increase or reduce the crushing size can be a complicated, labour-intensive and time-consuming task, in some cases, requiring two or more workers several hours of work to complete. Moreover, due to its complexity, such work tends not to be performed in the field and usually needs to be carried out at a maintenance/repair facility.
Based on the foregoing, there is a real need for a ruggedly built rock crusher that is powerful enough to crush relatively large volumes of hard rock in a short period of time. Preferably, the crusher mechanism of such a rock crusher would be configured to allow for the size of the crushed rock produced to be quickly and easily adjusted to suit particular field applications.